Small animal imaging is increasingly used in research and modeling of human disease. With this increase in small animal imaging, more and more small animals are processed. When imaging live specimens, such as mice, rats, guinea pigs, rabbits, pigs, etc., the physiology of the animal, such as the heart rate and temperature of the animal, is commonly monitored. To monitor the physiology of the animal, probes are secured to the animal. For example, electrocardiogram (ECG) probes are commonly secured to the animals' limbs. Unfortunately, these probes can be time consuming to position and attach to the animal. Also, the body position of the animal can have a significant effect on certain measured results. Moreover, measurement and imaging of the same animal is often repeated throughout the life of the animal in order to track changes such as tumor growth. Comparative and computer-aided image processing algorithms can also be used in tracking such changes. The repeatability of positioning of the animal is important when using such computer-aided image processing. Thus, it is desirable to consistently position the animals in identical positions for imaging and measurement.
Preparation of individual animals involves awkward and time-consuming work for the application of electrodes and temperature probes. Due to the size of some small animals, such as mice, this work is especially difficult and time-consuming. There are several different types of harnesses and jackets available for incorporating ECG probes. None of these devices, however, include a temperature measurement probe nor do they provide standardized positioning for the animals.
One example of a device that is used for holding a small animal, is an E-resp™ cradle available from SA Instruments, Inc, 65 Main Street, Stony Brook N.Y., 11790 (http://i4sa.com/newproducts.shtml). This device provides a holder for a mouse during testing. However, this cradle does not provide standardized positioning as only the main body portion of the mouse is supported. Also, ECG electrodes must still be attached to the limbs of the mouse, and there is no provision for monitoring the temperature of the mouse.
Another example of a device for holding a small animal is the Model 900M MRI, small animal stereotaxic instrument, available from David Kopf Instruments, 7324 Elmo Street, Tujunga Calif., 91042 (http://kopfinstruments.com/Stereotaxic/900M.htm). This device is a stereotaxic frame for stabilizing the head of the small animal, such as a rat, by inserting bars into the ears of the rat and thereby inhibiting movement of the rat's head. Clearly, this device stabilizes only the head of the animal and fails to provide a standardized positioning for the remainder of the rat body. Also, this device does not provide ECG electrodes or a thermocouple for monitoring the temperature of the rat.
Recent advances in MRI technology have allowed for the study of a number of small animals at one time, in a single MRI. For example, U.S. Pat. No. 6,549,797 to Bock et al., issued Apr. 15, 2003, the entire content of which is incorporated herein by reference, discloses a method and apparatus for simultaneous imaging of a plurality of objects using a common magnet. In the apparatus disclosed by Bock, sixteen mice are imaged concurrently. Thus, there is a clear need for efficient preparation of each animal.
Accordingly, it is an object of an aspect of the present invention to provide an animal positioning apparatus that obviates or mitigates at least some of the disadvantages of the prior art.